JP4876508B2 - Zoom lens - Google Patents

Description

  The present invention relates to a zoom lens for a single-lens reflex camera.

2. Description of the Related Art In recent years, zoom lenses having a plurality of focusing groups have been known for miniaturization and high performance of zoom lenses as camera lenses become autofocus (see, for example, Patent Document 1 and Patent Document 2). .
JP-A-5-341188 JP-A-6-3592

  However, the disclosure example of Patent Document 1 is a focusing method in which the first lens group and the second lens group are moved, and the movement amount of the first lens group is reduced, leading to reduction of the lens diameter. Since the first lens group, which is a lens group, is used for focusing, there is a problem that a large burden is applied to the autofocus mechanism.

  The disclosed example of Patent Document 2 is a focusing system having a so-called floating. However, the amount of movement of the second lens group in focusing is smaller than that of the movable lens group contributing to other focusing, particularly on the telephoto side. However, there is a problem that the second lens group having a high refractive index cannot be effectively used and is inefficient and it is difficult to ensure optical performance.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a zoom lens for a camera that has a small, lightweight, and good optical performance by a floating inner focus or rear / focus focusing method. And

In order to solve the above problems, the present invention has a plurality of lens groups and an aperture stop, and performs zooming from the wide-angle end state to the telephoto end state by changing the interval between the plurality of lens groups,
In order from the most object side, it has a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group,
During zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group increases, and the distance between the second lens group and the third lens group decreases.
The second lens group and at least one lens group located on the image side from the second lens group are a focusing lens group, and at least one lens group located on the image side from the second lens group is the nth lens group. According to the focal length state from the wide-angle end state to the telephoto end state as a lens group, at least one of the focusing lens groups is moved to focus from a long distance object to a short distance object,
A zoom lens characterized in that, when focusing from a long distance state to a short distance state, the entire second lens group is moved in the object direction and the following conditions are satisfied.

0.2 <(Xnw-X2w) / Xnw
0.5 <(X2t-Xnt) / X2t
−0.98 <M2t <−0.70
Where X2w is the amount of movement of the second lens group when focusing at a short distance in the wide-angle end state, and Xnw is the amount of movement of the n-th lens group excluding the second lens group when focusing at a short distance in the wide-angle end state. , X2t is the amount of movement of the second lens group when focusing at a short distance in the telephoto end state, and Xnt is the amount of movement of the nth lens group excluding the second lens group when focusing at a short distance in the telephoto end state; M2t: imaging magnification in the telephoto end state of the second lens group .

  According to the present invention, it is possible to provide a zoom lens for a camera which has a small size and light weight and good optical performance by a floating inner focus or rear / focus focusing method.

  Hereinafter, embodiments of the present invention will be described in detail.

  The zoom lens according to the embodiment of the present invention has a plurality of lens groups and an aperture stop, and performs zooming from the wide-angle end state to the telephoto end state by changing the interval between the plurality of lens groups, respectively. In order from the side, the first lens group having a positive refractive power, the second lens group having a negative refractive power, and a third lens group, the first lens group during zooming from the wide-angle end state to the telephoto end state And the distance between the second lens group is increased, the distance between the second lens group and the third lens group is decreased, and the second lens group and at least one lens group located on the image side from the second lens group are The focusing lens group has a configuration in which at least one of the focusing lens groups is moved from a long-distance object to a short-distance object in accordance with a focal length state from a wide-angle end state to a telephoto end state.

  The second lens group is suitable for incorporating a focusing mechanism because the lens diameter can be reduced as compared with other lens groups, particularly the first lens group. Furthermore, by moving at least one lens group as the focusing group in addition to the second lens group, fluctuations in imaging performance due to focusing are suppressed, and the moving range of each focusing group is made efficient and compact and lightweight. Can be realized.

In addition, it is desirable that the zoom lens according to the embodiment of the present invention satisfies the following conditional expression (1).
(1) 0.2 <(Xnw-X2w) / Xnw
Where X2w is the amount of movement of the second lens group when focusing at a short distance in the wide-angle end state, and Xnw is the amount of movement of the nth lens group excluding the second lens group when focusing at a short distance in the wide-angle end state. The sign of the movement amount is positive for the movement amount in the image plane direction.

  Conditional expression (1) defines the movement ratio of the focusing lens group other than the second lens group and the second lens group when focusing at a short distance in the wide-angle end state. Satisfying the conditional expression (1) makes it possible to effectively suppress the aberration between the first lens group and the second lens group in the wide-angle end state.

  If the lower limit value of conditional expression (1) is exceeded, the in-focus movement amount of the second lens group increases as the floating effect of the in-focus group decreases. As a result, the image plane variation from a long-distance object to a short-distance object becomes violent and coma becomes worse. Or, in the wide-angle end state, the distance between the first lens group and the second lens group must be secured wider than the movement distance (dead space) required for focusing. This enlarges the diameter of the front lens of the first lens group in order to secure off-axis luminous flux, which is not preferable because it obstructs the reduction in size and weight.

  In order to secure the effect of the present invention, it is preferable to set the lower limit of conditional expression (1) to 0.3.

It is desirable that the zoom lens according to the embodiment of the present invention satisfies the following conditional expression (2).
(2) 0.5 <(X2t-Xnt) / X2t
Where X2t is the amount of movement of the second lens group when focusing at a short distance in the telephoto end state, and Xnt is the amount of movement of the nth lens group excluding the second lens group when focusing at a short distance in the telephoto end state. The sign of the amount of movement is positive for the amount of movement in the image plane direction.

  Conditional expression 2 defines the movement ratio of the focusing lens group other than the second lens group and the second lens group when focusing at a short distance in the telephoto end state. By satisfying conditional expression (2), it is possible to reduce the deterioration of various aberrations and to effectively suppress the amount of movement of the lens groups other than the second lens group when focusing at a short distance in the telephoto end state.

  If the lower limit value of conditional expression (2) is exceeded, the floating effect of the focusing group decreases and the amount of movement of the focusing group other than the second lens group during focusing increases. As a result, the distance between the lens groups is increased to secure the amount of movement during focusing, which hinders reduction in size and weight. Further, an excessive movement amount at the time of focusing of the focusing group located on the image side from the second lens group is not preferable because spherical aberration fluctuations from an infinite distance to a close distance become severe.

  In order to secure the effect of the present invention, it is preferable to set the lower limit of conditional expression (2) to 0.8 in order to ensure the effect of the present invention.

  In the zoom lens according to the embodiment of the present invention, the second lens group moves in the image plane direction and the third lens group moves in the object direction during zooming from the wide-angle end state to the telephoto end state. Is desirable. In zooming from the wide-angle end state to the telephoto end state, the first lens unit and the third lens unit move in the object direction, so that the magnification variation can be efficiently performed while controlling the image plane variation.

  In the zoom lens according to the embodiment of the present invention, it is desirable that the absolute value of the movement amount of the second lens group is the minimum in the wide-angle end state when focusing from a long distance object to a short distance object. In the wide-angle end state, the movement of the second lens unit by focusing at a short distance is not preferable because it causes an increase in image plane fluctuation. In addition, movement of the nth lens unit other than the second lens unit due to short-distance focusing in the telephoto end state is not preferable because the spherical aberration variation becomes severe. Therefore, in the focus floating effect, it is preferable to increase the amount of movement of the second lens group on the telephoto side while suppressing the movement of the second lens group as much as possible on the wide angle side.

  In the zoom lens according to the embodiment of the present invention, the movement range of the second lens group when focused is in the variable power trajectory range from the wide-angle end state to the telephoto end state in the infinite focus state. desirable. The distance between the first lens group and the second lens group is narrower in the wide-angle end state in order to further increase the zooming effect and secure the peripheral luminous flux. In addition, in the case of a wide-angle zoom lens, the second lens unit having a negative refractive power is in a state in which the imaging magnification is set to be equal to or less than the same magnification. This tends to reduce the distance between the first lens group and the second lens group. In addition, the zoom lens system can be reduced in size and weight by minimizing the distance ratio of the second lens group when focusing at close distance and ensuring the distance (dead space) between the first and second lens groups when focusing at infinity. Can be planned. In order to further secure the effect of the present invention, it is desirable to fix the second lens group when focusing at a short distance in the wide-angle end state.

In the zoom lens according to the embodiment of the present invention, the entire second lens unit is moved in the object direction when focusing from the long distance state to the short distance state, and the following conditional expression (3) is satisfied. Is desirable.
(3) −0.98 <M2t <−0.70
Here, M2t is the imaging magnification in the telephoto end state of the second lens group.

  Conditional expression (3) defines the imaging magnification range of the second lens group in the telephoto end state suitable for focusing with the second lens group. If the upper limit of conditional expression (3) is exceeded, it will be difficult to obtain a sufficiently high zoom ratio. Or, coma aberration deteriorates and high optical performance cannot be obtained. If the lower limit of conditional expression (3) is exceeded, focusing in the telephoto end state becomes impossible, or the amount of focusing movement in the telephoto end state becomes too large to focus sufficiently close. . Or, spherical aberration deteriorates and high optical performance cannot be obtained.

〔Example〕
Each embodiment according to the present invention will be described below with reference to the drawings.

In the present embodiment, the aspheric shape is expressed by the following equation.
x = (h ² / r) / [1+ {1−κ (h / r) ² } ^1/2 ]
+ C4h ⁴ + C6h ⁶ + C8h ⁸ + C10h ¹⁰
Note that x is the displacement (sag amount) in the optical axis direction at the position of the height h from the optical axis with respect to the vertex of the surface, κ is the conic constant, and C4, C6, C8 and C10 are respectively 4, 6, 8, and 10th order aspherical coefficients, and r represents the radius of curvature (paraxial radius of curvature) of the reference spherical surface.

[First embodiment]
FIG. 1 is a lens configuration diagram of a zoom lens according to Example 1 of the present invention, where W represents a wide-angle end state, M represents an intermediate focal length state, and T represents a telephoto end state.

  In FIG. 1, the zoom lens according to the first example includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a negative refractive power. A third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, and a fifth lens group G5 having positive refractive power, and at the time of zooming from the wide-angle end state W to the telephoto end state T The distance between the first lens group G1 and the second lens group G2 is increased, and the distance between the second lens group G2 and the third lens group G3 is decreased.

  In focusing from a long distance object to a short distance object, the second lens group G2 and the third lens group G3 move in the object direction in the wide-angle end state W, and the second lens group in the intermediate focal length state M. The third lens group G3 moves in the object direction, and in the telephoto end state T, the second lens group G2 moves in the object direction.

  The first lens group G1 is composed of, in order from the object side, a cemented lens of a negative meniscus lens having a convex surface facing the object side and a biconvex positive lens, and a positive meniscus lens having a convex surface facing the object side.

  The second lens group G2 is composed of, in order from the object side, a negative meniscus lens having a concave surface facing the image plane I side, and a cemented lens of a biconcave negative lens and a positive lens having a convex surface facing the object side.

  The third lens group G3 is composed of, in order from the object side, a cemented lens of a biconcave negative lens and a positive lens having a convex surface facing the object side.

  The fourth lens group G4 includes, in order from the object side, an aperture stop S, a positive lens having a convex surface facing the image plane I, a biconvex positive lens, and a negative meniscus lens having a convex surface facing the image plane I. It consists of a cemented lens and a positive lens with a convex surface facing the object side.

  The fifth lens group G5 includes, in order from the object side, a negative meniscus lens having a concave surface facing the image surface I, a positive lens having a convex surface facing the object side, a biconvex positive lens, and a convex surface facing the image surface I It consists of a cemented lens with a negative meniscus lens.

  Table 1 below lists values of specifications of the zoom lens according to the second example. In the [Overall specifications] in the table, f represents a focal length, FNO represents an F number, and 2ω represents an angle of view (unit: degree). In [lens specifications], the first column is the lens surface number from the object side, the second column r is the radius of curvature of the lens surface, the third column d is the lens surface interval, and the fourth column νd is the d line (λ = Abbe number for 587.6 nm), the fifth column nd represents the refractive index for the d-line (λ = 587.6 nm). [Variable interval data] indicates the value of each variable interval between the focal length f and the close-in-focus state D0 of each focal length. Also, 1-POS is infinitely focused at the wide-angle end state, 2-POS is infinitely focused at the intermediate focal length state, and 3-POS is infinitely focused at the telephoto end state. POS is a short-distance focusing state at the wide-angle end state, 5-POS is a short-distance focusing state at the intermediate focal length state, and 6-POS is a short-distance focusing state at the telephoto end state. [Focus Movement Amount] indicates the movement amount of the lens group moved in a short distance focusing state from 4-POS to 6-POS, respectively. Further, r = “∞” represents a plane, and the refractive index nd = 0.0000 of air is omitted.

  In all the following specification values, “mm” is generally used as the focal length f, radius of curvature r, surface interval d and other lengths, etc. unless otherwise specified, but the optical system is proportional. Even if it is enlarged or proportionally reduced, the same optical performance can be obtained. Further, the unit is not limited to “mm”, and other appropriate units may be used. Furthermore, the description of these symbols is the same in the other examples.

(Table 1)
(Overall specifications)
f = 10.30-20.00-45.00
FNO = 3.7 ~ 4.6 ~ 6.1
2ω = 38.1〜22.6〜6.6

(Lens specifications)
rd vd nd
First lens group G1
1) 136.0279 1.400 25.35 1.805182
2) 56.7572 14.000 60.64 1.603110
3) -222.6619 0.100
4) 50.7262 8.000 60.64 1.603110
5) 164.6821 (d5)
Second lens group G2
6) -1839.1626 1.500 53.93 1.713000
7) 15.5706 7.000
8) -27.6703 1.500 57.53 1.670249
9) 16.5350 5.500 25.41 1.805182
10) 617.7097 (d10)
Third lens group G3
11) -32.8992 2.000 53.93 1.713000
12) 29.1477 4.000 27.61 1.755200
13) 457.0932 (d13)
Fourth lens group G4
14> ∞ 1.500 (Aperture stop S)
15) -1602.3397 3.800 64.10 1.516800
16) -29.8096 0.100
17) 58.7188 8.600 82.52 1.497820
18) -21.5259 1.000 33.89 1.803840
19) -70.9910 0.100
20) 31.1449 5.000 82.52 1.497820
21) -218.0092 (d21)
5th lens group G5
22) 55.7103 1.000 31.62 1.756920
23) 19.1692 4.998
24) 22.3894 6.000 54.55 1.514540
25) -134.2049 0.100
26) 29.6556 6.200 56.41 1.501370
27) -21.8584 1.000 45.37 1.796681
28) -83.2133 (Bf)

(Variable interval data)
1-POS 2-POS 3-POS 4-POS 5-POS 6-POS
F 10.3 20 45 10.3 20 45
D0 ∞ ∞ ∞ 500 500 500
d5 1.259 19.846 34.878 1.156 19.045 26.550
d10 44.246 22.170 4.615 44.202 22.570 12.944
d13 1.655 5.144 7.666 1.8018 5.544 7.666
d21 23.724 23.724 23.724 23.724 23.724 23.724
Bf 20.900 20.900 20.900 20.900 20.900 20.900

(In-focus movement amount)
4-pos 5-pos 6-pos
First lens group G1 0.000 0.000 0.000
Second lens group G2 -0.103 -0.801 -8.328
Third lens group G3 -0.147 -0.400 0.000
4th lens group G4 0.000 0.000 0.000
5th lens group G5 0.000 0.000 0.000
(+) = Image plane direction

(Values for conditional expressions)
(1) 0.30 (n = 3)
(2) 1.00 (n = 3)
(3) -0.974

  FIG. 2 shows various aberration diagrams of the zoom lens according to the first example in the infinite focus state, (a) shows various aberration diagrams in the wide-angle end state, and (b) shows in the intermediate focal length state. Various aberration diagrams are shown, and (c) shows various aberration diagrams in the telephoto end state. FIG. 3 shows various aberration diagrams of the zoom lens according to the first example in a short distance in-focus state (500 mm position from the first surface of the object side lens most), and (a) is a diagram of various aberrations in the wide-angle end state. (B) shows various aberration diagrams in the intermediate focal length state, and (c) shows aberration diagrams in the telephoto end state.

  In each aberration diagram, FNO is the F number, Y is the image height, A is the half field angle (unit: degree), H0 is the image height, d is the d-line (wavelength λ = 587.6 nm), and g is the g-line (wavelength λ). = 435.8 nm). In the astigmatism diagram, the solid line indicates the sagittal image plane, and the broken line indicates the meridional image plane. Furthermore, the description of these symbols is the same in the other examples.

  From each aberration diagram, it is clear that the zoom lens according to the first example has excellent imaging performance with various aberrations corrected well.

[Second Embodiment]
FIG. 4 is a lens configuration diagram of a zoom lens according to Example 2 of the present invention, where W is a wide-angle end state, M is an intermediate focal length state, and T is a telephoto end state.

  In FIG. 4, the zoom lens according to the second example includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a positive refractive power. And a fourth lens group G4 having a positive refractive power, and the distance between the first lens group G1 and the second lens group G2 upon zooming from the wide-angle end state W to the telephoto end state T. Is increased and moved so that the distance between the second lens group G2 and the third lens group G3 decreases.

  In focusing from a long distance object to a short distance object, the third lens group G3 and the fourth lens group G4 move in the direction of the image plane I in the wide-angle end state W, and the second lens in the intermediate focal length state M. The group and the third lens group G3 move in the object direction, and in the telephoto end state T, the second lens group G2 moves in the object direction.

  The first lens group G1 is composed of, in order from the object side, a cemented lens of a negative meniscus lens having a convex surface facing the object side and a biconvex positive lens, and a positive meniscus lens having a convex surface facing the object side.

  The second lens group G2 includes, in order from the object side, a negative meniscus lens having a concave surface directed toward the image plane I, a biconcave negative lens, a biconvex positive lens, and a biconcave negative lens. .

  The third lens group G3 includes, in order from the object side, an aperture stop S, two biconvex positive lenses, a positive lens having a convex surface facing the object side, and a negative meniscus lens having a convex surface facing the image surface I side. Become.

  The fourth lens group G4 includes, in order from the object side, a biconvex positive lens, a negative meniscus lens having a convex surface directed toward the object side, a cemented lens of a biconvex positive lens, and a biconcave negative lens Become.

  Table 2 below shows values of specifications of the zoom lens according to the second example.

(Table 2)
(Overall specifications)
f = 29.0-50.1-180.00
FNO = 3.8 ~ 4.6 ~ 6.2
2ω = 38.1〜22.6〜6.6

(Lens specifications)
rd vd nd
First lens group G1
1) 117.8863 2.000 23.83 1.846660
2) 55.9329 9.400 69.99 1.490000
3) -349.3659 0.150
4) 44.6073 6.148 51.41 1.687921
5) 162.0763 (d5)
Second lens group G2
6) 122.2354 1.200 53.42 1.726000
7) 13.9131 5.800
8) -35.9277 1.100 46.58 1.804000
9) 78.7412 0.100
10) 28.3377 4.600 23.83 1.846660
11) -39.8083 0.710
12) -29.5887 1.100 40.97 1.883000
13) 120.8448 (d13)
Third lens group G3
14> ∞ 0.000 (aperture stop S)
15) 30.9446 3.000 69.71 1.517280
16) -162.5684 0.120
17) 35.1050 2.000 70.45 1.487490
18) -340.7562 0.120
19) 48.8306 2.000 54.7 1.729160
20) 127.9327 1.494
21) -32.2027 1.200 25.46 1.805180
22) -255.4997 (d22)
Fourth lens group G4
23) 37.7834 4.000 64.14 1.516330
24) -28.4187 0.200
25) 116.1156 1.200 44.87 1.744000
26) 14.1308 3.421 49.86 1.623779
27) -66.9444 1.330 (Aspherical)
28) -62.4193 1.500 53.42 1.726000
29) 52.1176 (Bf)

(Aspherical data)
Surface κ C4 C6 C8 C10
27 1.0000 3.97370E-05 1.03890E-07 -4.69080E-10 6.28920E-12

(Variable interval data)
1-POS 2-POS 3-POS 4-POS 5-POS 6-POS
F 29 50 180 29 50 180
D0 ∞ ∞ ∞ 1000 1000 1000
d5 1.000 12.997 35.495 1.000 12.140 30.404
d13 17.924 12.431 1.000 19.134 13.173 6.092
d22 6.179 3.656 1.000 6.516 3.710 1.000
Bf 44.150 55.382 76.633 42.603 55.444 76.633

(In-focus movement amount)
4-pos 5-pos 6-pos
First lens group G1 0.00 0.00 0.00
Second lens group G2 0.00 0.86 5.09
Third lens group G3 -1.21 0.12 0.00
Fourth lens group G4 -1.55 0.00 0.00
5th lens group G5 0.00 0.00 0.00
(+) = Image plane direction

(Values for conditional expressions)
(1) 1.00 (n = 3), 1.00 (n = 4)
(2) 1.00 (n = 3)
(3) -0.889

  FIGS. 5A and 5B show various aberration diagrams of the zoom lens according to the second example in the infinite focus state, FIG. 5A shows various aberration diagrams in the wide-angle end state, and FIG. 5B shows the aberration in the intermediate focal length state. Various aberration diagrams are shown, and (c) shows various aberration diagrams in the telephoto end state. FIG. 6 shows various aberration diagrams in the short distance focusing state (1000 mm position from the first surface of the object side lens most) of the zoom lens according to the second example, and FIG. 6A shows various aberration diagrams in the wide-angle end state. (B) shows various aberration diagrams in the intermediate focal length state, and (c) shows aberration diagrams in the telephoto end state.

  From the respective aberration diagrams, it is clear that the zoom lens according to the second example has excellent imaging performance with various aberrations corrected well.

[Third embodiment]
FIG. 7 is a lens configuration diagram of a zoom lens according to Example 3 of the present invention, where W is a wide-angle end state, M is an intermediate focal length state, and T is a telephoto end state.

  In FIG. 7, the zoom lens according to the third example includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a positive refractive power. A third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, and a fifth lens group G5 having positive refractive power. The distance between the first lens group G1 and the second lens group G2 increases and the distance between the second lens group G2 and the third lens group G3 decreases.

  In focusing from a long distance object to a short distance object, the second lens group G2 and the fifth lens group G5 move in the object direction in the wide-angle end state W, and the second lens group in the intermediate focal length state M. The fifth lens group G5 moves in the object direction, and in the telephoto end state T, the second lens group G2 and the fifth lens group G5 move in the object direction.

  The first lens group G1 is composed of, in order from the object side, a cemented lens of a negative meniscus lens having a convex surface facing the object side and a biconvex positive lens, and a positive meniscus lens having a convex surface facing the object side.

  The second lens group G2 includes, in order from the object side, a negative meniscus lens having a concave surface directed toward the image plane I side, and a cemented lens of a biconcave negative lens and a biconvex positive lens.

  The third lens group G3 includes, in order from the object side, a cemented lens of a biconcave negative lens and a biconvex positive lens.

  The fourth lens group G4 includes, in order from the object side, an aperture stop S, a positive lens having a convex surface facing the image plane I, a biconvex positive lens, and a negative meniscus lens having a convex surface facing the image plane I. It consists of a cemented lens and a positive lens with a convex surface facing the object side.

  In order from the object side, the fifth lens group G5 includes a negative meniscus lens having a convex surface directed toward the object side, a positive lens having a convex surface directed toward the object side, a positive lens having a biconvex shape, and a negative lens having a concave surface directed toward the object side. It consists of a cemented lens with a meniscus lens.

  Table 3 below shows values of specifications of the zoom lens according to the third example.

(Table 3)
(Overall specifications)
f = 11.0-20.0-45.0
Fno = 1.9-1.9-2.0
2ω = 27.78-14.91-6.76

(Lens specifications)
rd vd nd
First lens group G1
1) 169.5741 1.400 25.35 1.805182
2) 71.3523 10.673 60.64 1.603110
3) -298.0965 0.200
4) 55.0370 6.441 60.64 1.603110
5) 164.6821 (d5)
Second lens group G2
6) 276.1751 1.400 53.92 1.713000
7) 15.0178 4.338
8) -35.1977 1.400 57.53 1.670249
9) 20.3488 2.912 25.41 1.805182
10) 617.7092 (d10)
Third lens group G3
11) -37.2061 1.400 53.92 1.713000
12) 35.1058 2.168 27.61 1.755200
13) 457.0931 (d13)
Fourth lens group G4
14> ∞ 1.500 (Aperture stop S)
15) -880.8190 3.763 64.1 1.516800
16) -29.3302 2.270
17) 59.8754 5.048 82.51 1.497820
18) -22.7318 1.400 33.89 1.803840
19) -81.0084 6.974
20) 26.2089 4.021 82.51 1.497820
21) 1213.2552 (d21)
5th lens group G5
22) 47.0333 1.400 31.62 1.756920
23) 23.8352 0.718
24) 34.6255 2.697 54.55 1.514540
25) -63.0276 0.200
26) 34.3496 4.114 56.41 1.501370
27) -18.2910 8.000 45.37 1.796681
28) -83.2133 (Bf)

(Variable interval data)
1-POS 2-POS 3-POS 4-POS 5-POS 6-POS
F 11.0 20.0 45.0 -0.02046 -0.03251 -0.03096
D0 0.0 0.0 0.0 500.0 500.0 500.0
d5 2.000 25.773 43.749 1.898 25.075 23.507
d10 32.556 22.170 4.615 32.657 22.869 24.437
d13 4.269 5.010 7.000 4.269 5.010 5.010
d21 16.239 16.585 17.959 15.934 15.886 16.471
Bf 20.498 21.455 22.273 20.804 22.154 21.569

(In-focus movement amount)
4-pos 5-pos 6-pos
First lens group G1 0.000 0.000 0.000
Second lens group G2 -0.102 -0.699 -7.054
Third lens group G3 0.000 0.000 0.000
4th lens group G4 0.000 0.000 0.000
5th lens group G5 -0.306 -0.699 -0.353
(+) = Image plane direction

(Values for conditional expressions)
(1) 0.667 (n = 5)
(2) 0.950 (n = 5)
(3) -0.829

  FIGS. 8A and 8B show various aberration diagrams of the zoom lens according to the third example in the infinite focus state. FIG. 8A shows various aberration diagrams in the wide-angle end state, and FIG. 8B shows the aberration in the intermediate focal length state. Various aberration diagrams are shown, and (c) shows various aberration diagrams in the telephoto end state. FIG. 9 is a diagram illustrating various aberrations of the zoom lens according to the third example in a short distance in-focus state (1000 mm position from the first surface of the most object side lens), and FIG. (B) shows various aberration diagrams in the intermediate focal length state, and (c) shows aberration diagrams in the telephoto end state.

  From each aberration diagram, it is clear that the zoom lens according to the third example has excellent image forming performance with various aberrations corrected satisfactorily.

According to the present invention, it has a long back focus that can also be used for a digital single lens reflex camera,
It is possible to provide a zoom lens that is small and light and has good optical performance.

  As an embodiment of the present invention, a lens system having a four-group or five-group configuration is shown. However, a lens system in which an additional lens group is added to the four-group or five-group is equivalent to the effect of the present invention. Needless to say, it is a lens system. In addition, in the configuration within each lens group, it goes without saying that a lens group in which an additional lens is added to the configuration of the embodiment is an equivalent lens group in which the effects of the present invention are inherent. Further, the above-described embodiment is merely an example, and is not limited to the above-described configuration or shape, and can be appropriately modified and changed within the scope of the present invention.

1 is a lens configuration diagram of a zoom lens according to a first example of the present invention, where W represents a wide-angle end state, M represents an intermediate focal length state, and T represents a telephoto end state. FIG. 5A illustrates various aberration diagrams of the zoom lens according to the first example in the infinite focus state, FIG. 10A illustrates various aberration diagrams in the wide-angle end state, and FIG. 9B illustrates various aberration diagrams in the intermediate focal length state. , And (c) show various aberration diagrams in the telephoto end state. FIG. 9A shows various aberration diagrams in the short distance in-focus state (500 mm position from the first surface of the most object side lens) of the zoom lens according to the first example, and FIG. ) Shows various aberration diagrams in the intermediate focal length state, and (c) shows aberration diagrams in the telephoto end state. FIG. 4 is a lens configuration diagram of a zoom lens according to Example 2 of the present invention, where W is a wide-angle end state, M is an intermediate focal length state, and T is a telephoto end state. FIG. 8A shows various aberration diagrams of the zoom lens according to the second embodiment in the infinite focus state, FIG. 10A shows various aberration diagrams in the wide-angle end state, and FIG. 9B shows various aberration diagrams in the intermediate focal length state. , And (c) show various aberration diagrams in the telephoto end state. FIG. 8A shows various aberration diagrams of the zoom lens according to the second example in a short distance in-focus state (1000 mm position from the first surface of the object side lens most), FIG. ) Shows various aberration diagrams in the intermediate focal length state, and (c) shows aberration diagrams in the telephoto end state. FIG. 4 is a lens configuration diagram of a zoom lens according to a third example of the present invention, where W represents a wide-angle end state, M represents an intermediate focal length state, and T represents a telephoto end state. FIG. 9A shows various aberration diagrams of the zoom lens according to the third example in the infinite focus state, FIG. 10A shows various aberration diagrams in the wide-angle end state, and FIG. 9B shows various aberration diagrams in the intermediate focal length state. , And (c) show various aberration diagrams in the telephoto end state. FIG. 8A shows various aberration diagrams of the zoom lens according to the third example in a short-distance in-focus state (1000 mm position from the first surface of the most object side lens), and FIG. ) Shows various aberration diagrams in the intermediate focal length state, and (c) shows aberration diagrams in the telephoto end state.

Explanation of symbols

G1 First lens group G2 Second lens group G3 Third lens group G4 Fourth lens group G5 Fifth lens group S Aperture I Image surface

Claims (7)

Having a plurality of lens groups and an aperture stop, by changing the interval between the plurality of lens groups, respectively, to perform zooming from the wide-angle end state to the telephoto end state,
In order from the most object side, it has a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group,
During zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group increases, and the distance between the second lens group and the third lens group decreases.
The second lens group and at least one lens group located on the image side from the second lens group are a focusing lens group, and at least one lens group located on the image side from the second lens group is the nth lens group. According to the focal length state from the wide-angle end state to the telephoto end state as a lens group, at least one of the focusing lens groups is moved to focus from a long distance object to a short distance object,
A zoom lens characterized in that, when focusing from a long distance state to a short distance state, the entire second lens group is moved in the object direction and the following conditions are satisfied.
0.2 <(Xnw-X2w) / Xnw
0.5 <(X2t-Xnt) / X2t
−0.98 <M2t <−0.70
However,
X2w: the amount of movement of the second lens group when focusing at a short distance in the wide-angle end state,
Xnw: the amount of movement of the n-th lens group excluding the second lens group when focusing at a short distance in the wide-angle end state;
X2t: the amount of movement of the second lens group when focusing at a short distance in the telephoto end state,
Xnt: the amount of movement of the nth lens group excluding the second lens group when focusing at a short distance in the telephoto end state
M2t: Imaging magnification in the telephoto end state of the second lens group   2. The zoom lens according to claim 1, wherein when zooming from the wide-angle end state to the telephoto end state, the second lens group moves in the image plane direction, and the third lens group moves in the object direction. .   3. The zoom lens according to claim 1, wherein an absolute value of a moving amount of the second lens unit is minimum in a wide-angle end state when focusing from a long-distance object to a short-distance object.   4. The moving range of the second lens group during focusing is in a zooming orbit range from a wide-angle end state to a telephoto end state in an infinitely focused state. 5. Zoom lens described in 1. Wherein said n lens group, a zoom lens according to claim 1, any one of 4, wherein the third lens group. A fourth lens group on the image side of the third lens group;
Wherein said n lens group, a zoom lens according to claim 1, any one of 5, wherein the a fourth lens unit. The fourth lens group and the fifth lens group in order from the object side on the image side of the third lens group;
Wherein said n lens group, a zoom lens according to any one of claims 1 6, characterized in that said a fifth lens group.

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